Coiled tubing injector apparatus

ABSTRACT

A coiled tubing injector apparatus for use in inserting coiled tubing into a well, temporarily suspending the coiled tubing, and removing the coiled tubing from the well is described. The apparatus includes a base with a pair of spaced-apart carriages extending upwardly therefrom. The base is part of a frame positioned above a wellhead. The carriages each have a gripper chain drive system rotatably mounted thereon and movable therewith. An actuation and linkage system allows the carriages to move toward and away from one another in a lateral or transverse direction with respect to the superstructure and the base. Thus, the gripper chain systems comprises gripper chains that can be engaged or disengaged from the coiled tubing extending through the apparatus. A wetting fluid basin is positioned below the gripper chains, and support guides engage the coiled tubing below the gripper chains to prevent buckling of the coiled tubing. The gripper chain drive system includes idler sprockets mounted on an idler sprocket shaft. The position of first and second ends of the idler sprocket shaft are monitored, and may be adjusted to maintain a parallel relationship with a drive sprocket shaft on which are mounted drive sprockets supporting the gripper chain.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of application Ser. No. 10/143,469filed May 10, 2002 now U.S. Pat. No. 6,719,043.

BACKGROUND

After a well has been completed to produce oil or gas, it is necessaryto periodically service the well. There are many occasions when theservice procedure is carried out using coiled tubing. Such tubing isinserted into the wellhead through a lubricator assembly or stuffingbox. Typically, this is necessary because there is a pressuredifferential at the surface of the well and the atmosphere, which mayhave been naturally or artificially created, that serves to produce oilor gas or a mixture thereof from the pressurized well. The tubing thatis inserted into the well is normally inserted through a lubricatormechanism which provides a seal about the O.D. of the tubing for theretention of any pressure that may be present at or near the surface ofthe well. The tubing is inserted by a coiled tubing injector apparatuswhich generally incorporates a multitude of gripper blocks for handlingthe tubing as it passes through the injector. The tubing is flexible andcan therefore be cyclically coiled onto and off of a spool, or reel, bythe injector which often acts in concert with a windlass and a powersupply which drives the spool, or reel.

The injector utilizes a pair of opposed endless drive chains which arearranged in a common plane. These opposed endless drive chains are oftenreferred to as gripper chains because each chain has a multitude ofgripper blocks attached therealong. The gripper chains are driven byrespective drive sprockets which are in turn powered by a reversiblehydraulic motor. Each gripper chain is also provided with a respectiveidler sprocket to maintain each gripper chain within the common plane.Both the drive sprockets and idler sprockets are mounted on a commonframe wherein the distance between centers of all the sprockets areessentially of a constant distance from each other. That is, the drivesprockets are free to rotate, but are not free to move either verticallyor laterally with respect to each other. The idler sprockets are notfree to move laterally with respect to each other, but are verticallyadjustable within a limited range in order to set the amount of play ineach gripper chain. Such vertical adjustment is made by either amechanical adjusting means or a hydraulic adjusting means. Typically,for injectors having mechanical adjustment means, the adjustment is madewhen the injector is not in operation.

The opposed gripper chains, preferably via the gripper blocks,sequentially grasp the tubing that is positioned between the opposedgripper chains. When the gripper chains are in motion, each gripperchain has a gripper block that is coming into contact with the tubing asanother gripper block on the same gripper chain is breaking contact withthe tubing. This continues in an endless fashion as the gripper chainsare driven to force the tubing into or out of the wellbore, depending onthe direction in which the drive sprockets are rotated. Gripper blockssuch as those set forth in U.S. Pat. No. 5,094,340, issued Mar. 10,1992, to Avakov, which is incorporated herein by reference, may be used.

The gripper chain is provided with a predetermined amount of slack whichallows the gripper chain to be biased against the tubing to inject thetubing into and out of the wellbore. This biasing is accomplished withan endless roller chain disposed inside each gripper chain. Each rollerchain engages sprockets rotatably mounted on a respective linear bearingbeam, referred to herein as a linear beam. A linkage and hydrauliccylinder mechanism allows the linear beams to be moved toward oneanother so that each roller chain is moved against its correspondinggripper chain such that the tubing facing portion of the gripper chainis moved toward the tubing so that the gripper blocks can engage thetubing and move it through the apparatus. The gripper blocks will engagethe tubing along a working length of the linear beam.

Each gripper chain has a gripper block that contacts the tubing at thetop of the working length as a gripper block on the same chain isbreaking contact at a bottom of the working length of the linear beam.

The fixed distance between each set of drive sprockets and idlersprockets requires some significant lateral movement in the gripperchain when engaged by the roller chain on the corresponding linear beamin order to allow the gripper chains to engage the tubing by way of thegripper blocks. The reason for having the requisite amount of lateralplay in the gripper chains is to provide a limited amount of clearancebetween the gripper chains, upon moving the respective roller chainsaway from the vertical centerline of the injector, to allow the passageof tubing and tools having larger outside diameters or dimensions. Oneshortcoming in this design is that the required slack can often causemisalignment problems and even binding problems with the gripper chainsdue to having to accommodate ever increasing outside nominal dimensionsof downhole tools and wellhead equipment.

There are, within the art, injectors that can accommodate a variety ofoutside diameters of tubing while avoiding: chain misalignment, chainbinding tendencies, improper chain tension, gripper block marking orgouging, and other inherent design problems of prior injectors whichmanifest themselves when working with tubing, tools, and surfaceequipment having large nominal outside diameters. Examples of suchinjectors are disclosed in U.S. Pat. No. 5,553,668, issued Sep. 10,1996, to Council et al., and U.S. Pat. No. 6,209,634, issued Apr. 3,2001, to Avakov et al., both of which are incorporated herein byreference and assigned to the assignee of the present invention.

There are, however, other difficulties that are faced when utilizing aninjector to inject, suspend, or extract tubing from a wellbore. Duringoperation of an injector, the idler sprockets may move, so that thecenterline of the idler sprocket moves relative to the centerline of thedrive sprocket, and may no longer be parallel to the centerline of thedrive sprocket. There is a need for an apparatus that will allow thedistance between the drive sprockets and the idler sprockets to bemonitored and verified.

Generally, as provided herein, the wellbore in which the tubing isinjected will be pressurized, so that as the tubing is initiallyinserted through the injector and into the wellbore, the pressure willtend to resist injection of the tubing. The pressure in the wellattempts to push the tubing upwardly as the tubing is being injected,which causes buckling forces to be applied to the tubing between thelower end of the working length of the gripper chain and the point atwhich the tubing is engaged in the stuffing box or lubricator. Further,the tubing should be lubricated prior to entering the stuffing box.Presently, a wetting fluid is manually applied to the tubing after thetubing is spooled off the reel and prior to the time the tubing isengaged by the injector. Manual application of wetting fluid can behazardous to the environment, due to the nature of the wetting fluidsthat may be used, and may be dangerous to the workers applying thefluid.

It is also important that as the downward forces are applied to thetubing by the gripper chains and the gripping loads are applied to thetubing, the gripper chains remain parallel to one another, and resisttransverse movement. If the gripper chains move sideways relative to oneanother, the result can be less gripping force, and damage to the tubingand the injector.

SUMMARY

The present invention is directed to a coiled tubing injector apparatusfor use in inserting coiled tubing into a well, temporarily suspendingthe tubing in the well, and for extracting tubing from the well. Theinjector generally comprises a base, a carriage extending upward fromthe base, and a gripper chain drive system mounted in the carriage. Thebase is mounted on legs, or a superstructure, and is positioned above awellhead.

The carriage may be pivotally attached to the base, and is preferablylaterally movable with respect to the base. The gripper chain drivesystem is movable with the carriage, and is adapted to engage tubingextending through the superstructure. The carriage is preferably one ofa pair of spaced carriages which may be pivotally attached to andlaterally movable with respect to the base. The tubing will pass betweenthe spaced carriages and through the base along a preselectedcenterline, so that the tubing will pass between and be engaged by thegripper chain drive systems when the carriages are moved toward oneanother.

The base has a pair of attachment lugs extending upwardly therefrom. Theattachment lugs will mate with corresponding carriage lugs located at alower end of the carriages. The carriages are attached to the base witha load pin extending through the attachment lugs and correspondingcarriage lugs. The attachment lugs are slidably connected to the base,so that the carriages are laterally movable with respect to the base andeach other.

The gripper chain drive system comprises a drive shaft mounted on thecarriage, drive sprockets mounted on the drive shaft, an idler shaftmounted on the carriage, and idler sprockets mounted on the idler shaft.A gripper chain which includes a plurality of gripper blocks attachedthereto engages the drive and idler sprockets.

A roller chain system for supporting the gripper chain when it engagesthe tubing is also included. The roller chain system is mounted on apressure, or linear beam that is rigidly positioned in the carriage. Theroller chain system includes an upper mounting shaft mounted on thelinear beam, an upper roller sprocket mounted on the upper mountingshaft, a lower mounting shaft mounted on the linear beam, a lower rollersprocket located on the lower mounting shaft, and a roller chain engagedwith the upper and lower roller sprockets. Each linear beam has aworking length defined thereon to support the gripper chain. When thecarriages are moved so that the gripper chains engage the tubing, thegripper chain will engage the tubing along the working length of thelinear beam, and a corresponding working length of the gripper chain. Inone embodiment of the invention, the linear beam may have a raised face,and the roller chain may be notched, to limit lateral movement of theroller chain with respect to the linear beam, and to limit lateralmovement of the gripper chain with respect to the roller chain.

The injector includes a means for moving the carriages laterally, whichmay comprise a plurality of hydraulically actuated gripper cylinders.When the gripper cylinders are actuated to move the carriages toward oneanother, the gripper chains will engage the tubing. The injectorincludes a pair of support guides attached to and movable with thecarriages. The support guides engage the tubing below the lower end ofthe working length of the gripper chain, and have a length sufficient toresist buckling loads. The support guides preferably span substantiallythe distance between the lower end of the working length and the exit ofthe base of the injector. The support guides preferably are comprised ofan ultrahigh molecular weight material, and have a profile that matchesthe profile of the gripper blocks.

The injector includes a wetting fluid basin through which the tubingpasses prior to entering the stuffing box. The basin is positioned belowthe lower end of the working length of the gripper chain, and ispreferably defined at least partially by the base of the injector.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows the coiled tubing injector apparatus of thepresent invention in position for inserting coiled tubing into anadjacent wellhead.

FIG. 2 shows a front view of the carriages of the injector of thepresent invention.

FIG. 3 shows a side view of the injector of the present invention.

FIG. 4 shows a partial front view and a partial cross section of thecarriages with a portion of the outer plate removed.

FIG. 5 shows a partial schematic looking at the inner side of a carriagefrom the center of the injector with the gripper and roller chainsremoved.

FIG. 6 shows a view from line 6—6 of FIG. 3.

FIG. 7 shows a view of a linear beam.

FIG. 8 shows the working or bearing face of a linear beam without theroller chain.

FIG. 9 shows a view taken from line 9—9 of FIG. 6.

FIG. 10 shows a view taken from line 10—10 of FIG. 6.

FIGS. 11 and 12 show section views from lines 11—11 and 12—12,respectively, of FIG. 2.

FIG. 13 shows the base of the present invention.

FIG. 14 shows a view from line 14—14 of FIG. 13.

FIG. 15 shows a view from line 15—15 of FIG. 13.

FIG. 16 shows a view from line 16—16 of FIG. 15.

FIG. 17 shows a view from line 17—17 of FIG. 15.

FIGS. 18 and 19 show detailed views of the carriage lug of the presentinvention.

FIGS. 20A and 20B show perspective views of a portion of the chain ofthe present invention.

FIGS. 21 and 22 show side and front views of the lower end of thecarriages.

FIG. 23 is a cross section of an alternative arrangement for a linearbeam face plate and roller chain.

FIG. 24 is a view from line 24—24 of FIG. 4.

FIG. 25 is a view from line 25—25 of FIG. 2.

DESCRIPTION

Referring now to the drawings, and more particularly to FIG. 1, thecoiled tubing injector apparatus of the present invention is shown andgenerally designated by the numeral 10. Injector 10 is shown positionedabove a wellhead 12 of a well 13 at a ground surface or subsea floor 14.A lubricator or stuffing box 16 is connected to the upper end ofwellhead 12.

Tubing 18, having a longitudinal central axis 20 and an outer diameteror outer surface 22, is supplied on a large drum, or reel 24 and istypically several thousand feet in length. Tubing 18 of sufficientlength, such as 10,000 feet or greater, may be inserted into the well 13either as single tubing, or as tubing spliced by connectors or bywelding. The outer diameters of the tubing 18 typically range fromapproximately one inch (2.5 cm) to approximately five inches (12.5 cm).The disclosed injector 10 is readily adaptable to even larger diameters.Tubing 18 is normally spooled from drum 24 typically supported on atruck (not shown) for mobile operations.

Injector 10 is mounted above wellhead 12 on legs 26. A guide framework28 having a plurality of pairs of guide rollers 30 and 32 rotatablymounted thereon extends upwardly from injector 10.

Tubing 18 is supplied from drum 24 and is run between rollers 30 and 32.As tubing 18 is unspooled from drum 24, generally it will pass adjacentto a measuring device, such as wheel 34. Alternatively, the measuringdevice may be incorporated in injector 10, such as described in U.S.Pat. No. 5,234,053, issued Aug. 10, 1993, to Connell.

Rollers 30 and 32 define a pathway for tubing 18 so that the curvaturein the tubing 18 is slowly straightened as it enters injector 10. Aswill be understood, tubing 18 is preferably formed of a material whichis sufficiently flexible and ductile that it can be curved for storageon drum 24 and also later straightened. While the material is flexibleand ductile, and will accept bending around a radius of curvature, itruns the risk of being pinched or suffer from premature fatigue failureshould the curvature be severe. Rollers 30 and 32 are spaced such thatstraightening of the tubing 18 is accomplished wherein the tubing 18 isinserted into the well 13 without kinks or undue bending on the tubing18. However, the disclosed injector 10 can be used for injecting,suspending, or extracting any generally elongated body. All of this isdone in a manner known in the art.

Referring now to FIGS. 2-18, the details of injector 10 will bediscussed. Injector 10 includes a frame 36. Frame 36 has legs 38, rearsupports 40, and side supports 42. Injector 10 further comprises a base44 which makes up a part of frame 36, and a pair of substantiallysimilar carriages 46 extending upward therefrom. Each carriage 46 has acarriage lug 50 extending downward from a lower end thereof. Thecarriage lugs 50 mate with a pair of attachment lugs 52 which extendupwardly from base 44 and which are slidable relative thereto asexplained more fully herein. FIG. 14 shows attachment lugs 52 which mayinclude a lug base 54 having upper and lower surfaces 56 and 58,respectively, and an attachment portion 60 extending upward therefrom. Aload pin 62, having a center or longitudinal central axis 64 extendsthrough each carriage lug 50 and the corresponding attachment lug 52 sothat the carriages 46 are pivotally attached to the base 44. Theinjector 10 also includes a means 66 for moving the carriages laterallywith respect to one another and with respect to the base 44. Theinjector 10 has a front, or forward side 68, and a back, or rear side70.

Carriages 46 comprise a first or right side carriage 72 and a second orleft side carriage 74. Carriages 72 and 74 will move towards and awayfrom each other when means for moving 66 is actuated. Carriages 72 and74 are substantially similar in that, as seen in FIG. 2, carriages 72and 74 are mirror images of one another. Right side carriage 72comprises first outer plate 76 and second outer plate 78. Outer plates76 and 78 are mirror images of one another. First outer plate 76 mayinclude a rectangular cutout 80 at or near a lower end 82 thereof. Apair of bosses 84 extend along the sides 86 of rectangular cutout 80.First outer plate 76 has a mounting boss 88 at an upper end 90 thereof.

Second outer plate 78, being a mirror image of first outer plate 76,likewise includes a rectangular cutout 92 at or near a lower end 91thereof and a pair of bosses 94 extending downwardly along sides 96 ofrectangular cutout 92. Second outer plate 78 has a mounting boss 98 atan upper end 100 thereof. First outer plate 76 is the forward outerplate of right side carriage 72 and second outer plate 78 is the rearouter plate. Because outer plates 76 and 78 are mirror images, andbecause right and left side carriages 72 and 74, respectively, aremirror images, the forward outer plate of left side carriage 74 issubstantially identical to, and may be comprised of, second outer plate78, which is the rear outer plate of right side carriage 72. Likewise,the rear outer plate of left side carriage 74 is substantially identicalto, and may be comprised of, first outer plate 76. A back plate 102 isconnected to outer plates 76 and 78. Back plate 102 may be connectedusing bolts or other means known in the art. For instance, as shown inFIG. 2, the back plate 102 may have lugs 104 extending inwardlytherefrom so that bolts extending through the outer plates 76 and 78 maybe attached thereto.

Each carriage 46 also includes a gripper chain drive system 106 and aroller chain drive system 108. Referring to FIGS. 4 and 5, gripper chaindrive system 106 includes a pair of spaced gripper chain drive sprockets110 rotatably disposed in the carriage 46. Drive sprockets 110 aremounted on a drive sprocket shaft 112 having a centerline, orlongitudinal central axis 113 corresponding to, or collinear with, anaxis of rotation of the drive sprockets 110. As better seen in FIG. 12,drive sprocket shaft 112 extends through the mounting boss on theforward side 68 of the injector 10 and into a flanged bearing 114. Abearing adapter 116 is also included and is attached to the mountingboss, which in FIG. 12 is mounting boss 98. The drive sprockets 110 aredriven by a reversible hydraulic motor 118 attached to each carriage 46on the back side 70 of the injector 10. Hydraulic motor 118 is of a typeknown in the art and is driven by a planetary gear and has an integralbrake. Thus, hydraulic motor 118 can inject, retract, or suspend tubing18 in the well 13. Drive sprocket shaft 112 may be keyed or otherwiseconnected to drive sprockets 110, so that rotation of drive sprocketshaft 112 will rotate drive sprockets 110.

Gripper chain drive system 106 also includes a pair of spaced gripperchain idler sprockets 120 which are rotatably disposed in the lower endof each carriage 46. Idler sprockets 120 are mounted on idler sprocketshaft 122, having a centerline, or longitudinal central axis 119corresponding to, or collinear with, an axis of rotation of the idlersprockets 120. In the embodiment shown, the idler sprocket shaft 122 andidler sprockets 120 are one piece. However, idler sprocket shaft 122 maybe keyed or otherwise connected to idler sprockets 120 so that idlersprocket shaft 122 and idler sprockets 120 will rotate together. As bestseen in FIG. 11, gripper chain tensioners 124 are connected to theopposite ends of idler sprocket shaft 122. Tensioners 124 are mounted onbosses 84 and 94 of first outer plate 76 and second outer plate 78,respectively. Tensioners 124 are mounted so that they can be verticallyadjusted within rectangular cutouts 80 and 92. A gripper chain 126 isengaged with drive sprockets 110 and idler sprockets 120 in eachcarriage 46. Gripper chain 126 may be of a kind known in the art and hasa plurality of outwardly facing gripper blocks 128 disposed thereon.

Gripper blocks 128 are adapted for engaging tubing 18 and moving itthrough injector 10. Gripper blocks 128 may be like those set forth inU.S. Pat. No. 5,853,118, issued Dec. 29, 1998, to Avakov or U.S. Pat.No. 6,230,955, issued May 15, 2001, to Parks, both of which areincorporated herein by reference and assigned to the assignee of thepresent invention. When actuating means 66 is actuated to move carriages72 and 74 together, a gripping force is applied to tubing 18 by gripperblocks 128.

As schematically shown in FIG. 20B, gripper blocks 128 have an innerface 129 defining an inner profile. The gripper blocks 128 will contactouter diameter 22 of tubing 18 on both sides of longitudinal centralaxis 20.

As set forth herein, carriage lug 50 is rigidly mounted to and extendsdownwardly from each carriage 72 and 74. As shown in FIGS. 18 and 19,each carriage lug 50 has a pair of ears 130 extending outwardlytherefrom. Ears 130 have openings 131 defined therein. Carriage lugs 50each include a pair of spaced carriage mounting lugs 132.

Tensioners 124 provide for the adjustment of the position of idlersprocket shafts 122 so that the proper tension on gripper chains 126 maybe maintained, and so that the proper distance, and parallelrelationship between idler sprocket shafts 122 and drive sprocket shafts112 may be maintained. Tensioner 124 includes a bearing portion 134 andhas a tensioning shaft 136 mounted to and extending downwardly frombearing portion 134. Idler sprocket shafts 122 are mounted in bearingportion 134. Tensioning shafts 136 have an upper end 135 that isconnected to a mounting lug 137 positioned in an opening 138 in bearingportion 134. Tensioning shafts 136 extend through openings 131 in theears 130 on carriage lug 50. A spring 140 is disposed around thetensioning shaft 136 below ears 130. Spring 140 may extend upwardlythrough openings 131 in ears 130 and be captured by a guide sub 141,which is slotted to receive and move along bosses 84 and 94 on outerplates 76 and 78, respectively, as shown in FIG. 24. The position ofidler sprocket shaft 122, and thus the tension in gripper chain 126, canbe adjusted simply by rotating a nut 142 on the threaded end oftensioning shaft 136. Guide sub 141 may be fixed to ear 130 so thatrotation of nut 142 will move the end of the idler sprocket shaft 122 towhich the tensioning shaft 136 is connected.

Bearing portion 134 may comprise a circular boss 144 having a shoulder146 extending therefrom as shown in FIG. 25. Shoulder 146 has a groove148 therein. Boss 84 on first outer plate 76 is received in groove 148.Likewise, boss 94 on second outer plate 78 is received in groove 148.Thus, bearing portion 134, and idler sprocket shaft 122, which ismounted therein can be vertically adjusted while lateral movement of theidler sprocket shaft 122 with respect to outer plates 76 and 78 isrestricted. Shoulder 146 has a lower edge 149. Drive sprocket shaft 112has ends that may be referred to as first and second ends 112 a and 112b. Likewise, idler sprocket shaft 122 has first end 122 a and second end122 b. Bearing portions 134 may therefore be referred to as first andsecond housings 134, in which first and second ends 122 a and 122 b,respectively, are mounted. Ends 112 a and 122 a are those at the front,or forward side 68 of injector 10 while ends 112 b and 122 b are thoseat the back, or rear side 70 of injector 10. Centerlines 113 and 119have distances D1 and D2 therebetween at the ends 112 a and 122 a oncarriages 72 and 74, respectively. Centerlines 113 and 119 havedistances D3 and D4 therebetween at the ends 112 b and 122 b oncarriages 72 and 74, respectively. Distances D1, D2, D3, and D4 arepreferably identical and thus, centerlines 113 and 119 are preferablyparallel.

Drive sprocket shafts 112 are fixed in position relative to the outerplates 76 and 78. Idler sprocket shafts 122 are vertically adjustable sothat proper chain tension can be achieved. During initial installation,the distances D1-D4 are measured with, for example, a large set ofvernier calipers, and the idler sprockets 120 are positioned so thatdistances D1-D4 are identical. During operation, however, due to theforces applied to the gripper chain 126, it is possible that the idlersprocket shafts 122 will move so that centerlines 113 and 119 are nolonger in a parallel relationship. In other words, the distances D1 andD3 may no longer be identical. Likewise, the distances D1 and D3 may notbe identical to distances D2 and D4. To determine whether the ends ofthe idler sprockets 120 move during operation, a witness mark can beplaced on the outer plates 76 and 78. The witness marks may correspondto the lower edge 149 of shoulder 146 on bearing portion 134. Since theends 122 a and 122 b of idler sprocket shaft 122 are fixed in thebearing portion 134, bearing portion 134 will move with the ends 122 aand 122 b. Thus, any movement can be detected by visually inspecting theinjector 10 to determine if lower edge 149 has moved with respect to thewitness mark on the outer plates 76 and 78. A scale S with a pluralityof marks thereon may be attached to bosses 84 and 94 on outer plates 76and 78 of carriages 72 and 74, respectively. The marks on each scale Scan be graduated by any desired increment. The witness markcorresponding to the position of the lower edge 149 can be placed on allfour scales S to note the positions of ends 122 a and 122 b on both ofcarriages 72 and 74, or can be placed on the outer plates 76 and 78 nextto the scales S. The position of ends 122 a and 122 b can be monitoredby visually checking the position of lower edge 149 to determine if ithas moved from its initial position. The distances D1-D4 can continuallybe manipulated if changes in the positions of the centerlines 119 occursimply by rotating nut 142 so that the parallel relationship betweencenterlines 113 and 119 is restored and so that the distances D1-D4 areidentical, or at least substantially identical. Damage to the gripperchains 126 and to other equipment due to chain misalignment can be atleast minimized, by continually monitoring position of the ends 122 aand 122 b of the idler sprockets 120, and by moving the ends 122 a and122 b, as necessary to maintain desired distances D1, D2, D3, and D4,and to maintain a parallel relationship between centerlines 113 and 119.

The roller chain drive system 108 is rigidly positioned in each carriage46 between outer plates 76 and 78. Roller chain drive system 108includes a linear or pressure beam 150 rigidly fixed to the outer plates76 and 78 of the carriage 46. The linear beam 150 is shown in FIGS. 7and 8. Linear beam 150 may be comprised of a linear beam frame 152 witha bearing plate 154 attached thereto. Bearing plate 154 has a planarface 155. Linear beam frame 152 has side webs 156 which will nestbetween outer plates 76 and 78 of the carriage 46, respectively. Linearbeam 150 may be rigidly attached to the carriage 46 with bolts extendingthrough outer plates 76 and 78 and side webs 156. A working length 158is defined on the linear beam 150. Working length 158 has upper andlower ends 157 and 159, respectively. Linear beam 150 has upper andlower ends 164 and 166, respectively. A pair of spaced upper, or firstroller chain sprockets 168 are rotatably disposed on upper end 164, anda pair of spaced second, or lower roller chain sprockets 170 arerotatably disposed on lower end 166 of the linear beam 150. A rollerchain 172 engages upper and lower roller chain sprockets 168 and 170,respectively. Roller chain 172 is supported on planar face 155 ofbearing plate 154. Roller chain 172 has an outer side 173 which willengage an inner side 175 of gripper chain 126. The roller chainsprockets 168 and 170 may be mounted on bearings 174 supported by shafts176. Lower roller chain sprockets 170 incorporate a tensioner (notshown), of a type known in the art to keep the proper tension on rollerchain 172.

An alternative linear beam 150 and roller chain 172 arrangement is shownin FIG. 23, which is a cross sectional view from line 23—23 on FIG. 8.As shown therein, in the alternative arrangement the linear beam 150,referred to as linear beam 150 a, may have a bearing plate which will bereferred to as a bearing plate 154 a. Bearing plate 154 a has a raisedface 155 a. A notched roller chain 172 a is supported on raised face 155a. Raised face 155 a is received in notches 171 a defined in the rollersof notched roller chain 172 a. Gripper blocks 128 are likewise receivedin notches 171 a. In the alternative embodiment shown in FIG. 23, thenotched roller chain 172 and the gripper chain 126 will be resistant tolateral loads since raised face 155 a will prevent or at least limit thelateral movement of notched roller chain 172 a. Lateral movement ofgripper chain 126 is likewise resisted since gripper blocks 128 arereceived in notches 171 a. Such an arrangement lessens the likelihoodthat the gripper chains 126 will become misaligned, and also lessens thelikelihood of any side loading of the gripper chains 126 and the rollerchains 172 a.

As shown in FIGS. 13 and 14, attachment lugs 52 are slidably mounted tobase 44. Base 44 has an opening 180 defined therein for tubing 18 topass therethrough. As will be explained in more detail hereinbelow,opening 180 comprises a portion of a basin 182 for holding a wettingfluid. Attachment lugs 52 are slidably received in tracks 186, which arerigidly attached to base 44. Carriages 72 and 74 are thus slidabletoward and away from each other to accommodate various sizes of tubing18.

Means for moving 66 comprises a plurality of, and preferably four,hydraulic actuator cylinders 184. The injector 10 may include uppercylinders 185 and lower cylinders 188. Actuator mounting plates 190 and192 having clevis lugs 191 and 193, respectively, extending therefromare rigidly mounted to outer plates 76 and 78. The ends of cylinders 185and 188 are attached to clevis lugs 191 and 193, respectively. Actuatormounting plates 190 and 192 may be attached utilizing bolts or othermeans known in the art which extend through the actuator mounting plates190 and 192 and the outer plates 76 and 78 of carriages 72 and 74,respectively.

The injector 10 also includes upper and lower equalizer linkages 200 and202, respectively, on both the front 68 and back 70 of carriages 72 and74. Upper equalizer linkage 200 includes a center link 204, an upperouter link 206, and a lower outer link 208. Center link 204 is pivotallymounted to a laterally extending guide plate 210 which is rigidlyattached at its ends to side supports 42 of frame 36. The outer ends ofthe upper and lower outer links 206 and 208, respectively, are mountedto slider plate assemblies 212 and 214 as better seen in FIGS. 6, 9, and10. Slider plate assembly 212 includes an upper slider plate 216 and alower slider plate 218. Upper and lower slider plates 216 and 218,respectively, are mounted to the carriages 72 and 74 utilizing fasteners220. Bearings 222 are mounted on fasteners 220 between upper and lowerslider plates 216 and 218, respectively, and engage an inner side 224 ofguide plate 210. Slider plate assembly 212 also includes bearings 226which are mounted between upper and lower slider plates 216 and 218,respectively, using fasteners 228. Bearings 226 engage an outer edge 230of guide plate 210.

Slider plate assembly 214 is arranged similar to slider plate assembly212 and thus includes upper and lower slider plates 232 and 234,respectively. Upper and lower slider plates 232 and 234, respectively,are mounted to the carriages 72 and 74 utilizing fasteners 236. Bearings238 are mounted on fasteners 236 between upper and lower slider plates232 and 234, respectively, and engage the inner side 224 of guide plate210. Slider plate assembly 214 also includes bearings 240 mountedbetween upper and lower slider plates 232 and 234, respectively, usingfasteners 242. Bearings 240 engage outer edge 230 of guide plate 210.The height of bearings 222, 226, 238, and 240 are substantiallyidentical and is such that there is clearance between the slider plates232 and 234 and guide plates 210. Each of the bearings 222, 226, 238,and 240 engage the sides of guide plates 210 so that when actuatorcylinders 184 move carriages 72 and 74 laterally, the carriages 72 and74 are supported by and slide along guide plates 210. Lower equalizerlinkage 202 is substantially identical to upper equalizer linkage 200and includes the components set forth above.

As shown in FIGS. 9 and 10, upper outer link 206 is connected to upperslider plate 232. Upper outer link 206 is connected utilizing a pair offasteners 244 and a pin 246 extending therebetween. Pin 246 extendsthrough an opening in the end of upper outer link 206. In like manner,lower outer link 208 is connected utilizing a pair of fasteners 248 witha pin 250 extending therebetween through an opening in the end of lowerouter link 208. Center link 204 is connected at centerline 251 of theinjector 10 so that when the actuator cylinders 184 are actuated, eachcarriage 46 will move an equal distance away from or toward centerline251. By utilizing upper and lower equalizer linkages 200 and 202,respectively, on both the front 68 and back 70 of carriages 72 and 74,the proper alignment of carriages 72 and 74 is maintained. Thearrangement restrains carriages 72 and 74 to prevent, or at least limit,deflection that might otherwise be caused by the clamping forces appliedto tubing 18.

In operation, when it is desired that tubing 18 be lowered, raised, orsuspended in the well 13, actuator cylinders 184 will be actuated untilgripper blocks 128 engage tubing 18. Gripper chains 126 will engagetubing 18 along working length 158 of the linear beams 150 and acorresponding working length 252 of the chain. Thus, gripper chain 126will first contact the tubing 18 at upper end 157 of the working length158 of linear beam 150, and the contact between the tubing 18 andgripper chains 126 will break as the tubing 18 passes lower end 159 ofworking length 158. As set forth previously, a gripper chain utilizingblocks of the type shown in U.S. Pat. No. 5,094,340 to Avakov ispreferably utilized. Referring to FIGS. 20A and 20B, the gripper chains126 may thus be comprised of outer links 300 and gripper blocks 128. Theouter links 300 and the gripper blocks 128 are connected to form anendless chain utilizing linking pins 302 which extend through the outerlinks 300 and the gripper blocks 128.

When tubing 18 is engaged by gripper blocks 128, support guides 254 willalso engage tubing 18. Support guides 254 are positioned so that thesupport guide 254 in each of carriages 72 and 74 will engage tubing 18when gripper blocks 128 on gripper chains 126 engage tubing 18.Referring to FIGS. 21 and 22, support guides 254 have an upper end 256,a lower end 258, and define a length 260. Length 260 is sufficient toresist buckling loads that may be applied to tubing 18 as it is injectedinto the well 13. Support guides 254 will engage the tubing 18 at apoint just below working length 252. As will be explained in more detailhereinbelow, length 260 is such that support guide 254 extends from justbelow the point where tubing 18 is disengaged from gripper chains 126downwardly into basin 182 so that it extends downwardly to almost alower end of the base 44. Support guide 254 comprises a slide or guideelement 262 having a face 263 mounted in a support guide housing 264.Support guide housing 264 may be generally semi-cylindrical in shape,and may have grooves 265 defined therein for receiving ridges 267defined by slide 262, to mount slide 262 in support guide housing 264.Slide 262 has an inner profile 266 that preferably matches the innerprofile of gripper blocks 128 used in gripper chain 126. Slide 262 ispreferably comprised of an ultrahigh molecular weight plastic material,and is preferably a polyethylene slide 262 so that when tubing 18 isengaged by support guide 254, tubing 18 will be supported but will slidethrough support guides 254. A mounting bracket 268 may be utilized toattach support guides 254 to outer plates 76 and 78 of carriages 72 and74. A pair of mounting brackets 268 may be utilized with each carriage72 and 74. Each mounting bracket 268 has a side flange 270 and a forwardflange 272. Forward flange 272 will extend from side flange 270 inwardlyto define a retaining flange 273 that covers face 263 of slide 262.Mounting blocks 274 may be positioned between outer plates 76 and 78 andbolts may be utilized to extend through the outer plates 76 and 78 andmounting blocks 274 to hold mounting brackets 268 in place which in turnholds support guides 254 in place.

Referring now to FIG. 13, base 44 has an upper surface 276 and comprisesfour legs 278 extending outwardly from opening 180. As shown in FIGS.15-17, the base 44 may have a generally I-shaped cross section withupper flanges 279, central web 280, and lower flanges 282. A sleeve 284comprises a portion of base 44 and may be attached by welding or anymeans known in the art. Sleeve 284 has an upper flange 286 and definesopening 180. Opening 180 defines a first inner diameter 288. Sleeve 284may have an inwardly extending flange 289 defining a second innerdiameter 290. FIG. 17 schematically shows in cross section stuffing box16 which may be a stripper/packer or other type of stuffing box known inthe art. A seal, or pack-off element 294 is disposed in stuffing box 16to sealingly engage the tubing 18 passing therethrough.

Basin 182 is defined by opening 180 and by opening 296 in stuffing box16. The lower end 298 of basin 182 is defined at pack-off element 294.Basin 182 holds a wetting fluid. Tubing 18 must pass through basin 182and thus through the wetting fluid. As is apparent, a uniformapplication of the wetting fluid will be applied which will aid in theinjection of tubing 18 through stuffing box 16 and other portions ofwellhead 12 into the well 13 therebelow. A uniform application of thewetting fluid will improve the life of tubing 18 and pack-off element294, and in addition provides for a much easier application of wettingfluid than any prior art method.

Injector 10 may further include a means for maintaining the fluid levelin the basin 182. Means for maintaining the fluid level in the basin 182may comprise a float valve 304 which is schematically shown in FIGS. 15and 17. Float valve 304 may comprise a housing 306 containing a floatswitch 308 connected to a float 310. Float switch 308 is electricallyconnected by wires 311 to a controller 312 which is in turn electricallyconnected to a pump 314. Pump 314 is connected to a wetting fluidreservoir 316. Float valve 304 is in fluid communication with basin 182through upper and lower hoses 315 and 317, respectively. When a level318 in housing 306, which as is understood will be equal to a level 318in basin 182, falls to a desired predetermined lower level, in this casethe level at which lower tube 317 is positioned in basin 182, floatswitch 308 will be actuated which will in turn actuate pump 314. Pump314 will then pump wetting fluid from reservoir 316 into basin 182 via aflow line until a desired upper level is reached, in this case the levelat which upper hose 315 is positioned in basin 182, at which time floatswitch 308 will automatically shut off, which will in turn automaticallyshut off pump 314. In this manner, level 318 in basin 182 can bemaintained between a desired upper level and a desired lower level. Thelower ends 258 of support guides 254 are shown in FIG. 17 and asexplained previously, length 260 of support guides 254 is such thatlower ends 258 are positioned at or near the lower end of opening 180defined in base 44. Thus, support guides 254 extend substantially fromthe lower end of working length 252 to a bottom, or lower end of base44.

It is understood that the foregoing description of the invention andillustrative drawings which accompany the same are presented by way ofexplanation only and that changes may be made by those skilled in theart without departing from the true spirit of this invention.

1. A coiled tubing injector apparatus comprising: a base; first andsecond carriages extending upwardly from the base, wherein each carriagehas first and second outer plates, and at least one of the first andsecond carriages is movable laterally with respect to the base; and agripper chain system mounted to the first and second outer plates ofeach carriage, wherein the gripper chain system comprises: a pair ofspaced gripper chain drive sprockets mounted on a drive sprocket shaftfor supporting a gripper chain, wherein the gripper chain is adapted toengage coiled tubing, and the drive sprocket shaft has a centerlinecorresponding to an axis of rotation of the drive sprockets; and a pairof spaced idler sprockets mounted on an idler sprocket shaft positionedbelow the gripper chain drive sprockets for supporting the gripperchain, wherein the idler sprocket shaft has a centerline correspondingto an axis of rotation of the idler sprockets, and the centerlines ofthe drive sprocket shaft and the idler sprocket shaft have a firstdistance therebetween at first ends of the drive sprocket shaft andidler sprocket shaft and a second distance therebetween at second endsof the drive sprocket shaft and idler sprocket shaft; wherein: the firstand second distances are initially substantially identical so that thecenterlines of the drive sprocket shaft and the idler sprocket shaft areparallel; the initial substantially identical first and second distancesare established by noting the position of the first and second ends ofthe idler sprocket shaft relative to witness marks on the first andsecond outer plates; and the position of the first and second ends ofthe idler sprocket shaft can be adjusted to maintain a parallelrelationship between the centerlines of the drive sprocket shaft and theidler sprocket shaft if the position of the first or second end of theidler sprocket shaft moves during operation.
 2. The coiled tubinginjector apparatus of claim 1 wherein the first and second carriages aremovable laterally with respect to the base.
 3. The coiled tubinginjector apparatus of claim 1 wherein: the first and second ends of theidler sprocket shafts are mounted in first and second housings; and theposition of the first and second ends of the idler sprocket shafts canbe monitored by checking the position of the first and second housingsrelative to the witness marks on the first and second outer plates. 4.The coiled tubing injector apparatus of claim 3 further comprising ascale fixed to the first and second outer plates, wherein: the initialposition of the first and second ends of the idler sprocket shaft can bedetermined relative to the scale; and the amount of any movement of theposition of the first and second ends of the idler sprocket shaft can bedetermined by monitoring the position of the first and second housingsrelative to the scale.
 5. The coiled tubing injection apparatus of claim4 wherein the scale is graduated, so that the amount of movement of thefirst and second ends is detectable, and so that the first and secondends can be moved the same distance to adjust a tension in the gripperchain and maintain a parallel relationship between the centerlines ofthe drive sprocket shaft and the idler sprocket shaft.
 6. The coiledtubing injector apparatus of claim 1 further comprising a wetting fluidbasin for holding a wetting fluid, wherein the wetting fluid basin ispositioned below the gripper chains so that the coiled tubing passesthrough the wetting fluid basin.
 7. A method for maintaining asubstantially parallel relationship between a drive sprocket axis ofrotation and an idler sprocket axis of rotation in a coiled tubinginjector, wherein the coiled tubing injector comprises first and secondouter plates having a pair of drive sprockets and idler sprocketslocated therebetween, the drive sprockets are mounted on a drivesprocket shaft, the drive sprocket shaft has a centerline collinear withthe drive sprocket axis of rotation, the idler sprockets are mounted onan idler sprocket shaft, and the idler sprocket shaft has a centerlinecollinear with the idler sprocket axis of rotation, wherein a gripperchain is supported on the drive sprockets and idler sprockets, themethod comprising the steps of: fixing the position of the drivesprocket shaft with respect to the first and second outer plates;positioning the idler sprocket shaft so that the centerline of the idlersprocket shaft is parallel to the centerline of the drive sprocket shaftand so that an initial distance between first and second ends,respectively, of the drive sprocket shaft and the idler sprocket shaft,is at a desired distance; placing a witness mark on the first and secondouter plates to mark the position of first and second ends of the idlersprocket shaft relative to the first and second outer plates; monitoringthe position of the first and second ends of the idler sprocket shaftrelative to the witness marks; and adjusting the position of the idlersprocket shaft to maintain the parallel relationship between the idlersprocket shaft centerline and the drive sprocket shaft centerline if thefirst or second end of the idler sprocket shaft moves relative to thewitness mark.
 8. The method of claim 7 further comprising the steps of:attaching scales to the first and second outer plates, wherein eachscale has a plurality of marks thereon; and measuring the amount ofmovement of the first and second ends of the idler sprocket shaft on thescales; wherein the adjusting step further comprises the step of movingthe first and second ends of the idler sprocket shaft to maintain theparallel relationship based on the measured amount of movement.
 9. Themethod of claim 8 further comprising the step of adjusting the tensionin the gripper chain supported by the drive and idler sprockets.
 10. Themethod of claim 8 wherein the measuring step further comprises the stepof measuring the amount of movement of first and second housings inwhich the first and second ends of the idler sprocket shaft are mounted.11. The method of claim 8 wherein the adjusting step is performed whilethe gripper chains are stationary.
 12. The method of claim 8 furthercomprising the step of repeating the measuring and adjusting steps asnecessary to maintain the parallel relationship.